Aerosol wetting agents in blueprint coatings



Patented July 30, 1,940

COATING Garnet Philip Ham, 01d Greenwich, and Robert Bowling Barnes, Stamford, Conn, assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application August 20, 1938,

' Serial N0. 225,904

5 Claims.

This invention relates to methods of coating blueprint paper.

Blueprint paper and similar papers such as, forexample, Van Dyke'negative paper, require coatmg of the paper with an-aqueous solution of the sensitizing agent. Two of the important characteristics of a good blueprint coating are speed and latitude; that is to say, the exposure time which is required togive sufliciently dark backgrounds for ordinary reproduction and the range I of exposure through which tones of adequate color can be obtained. The attempt to increase speed of blueprint papers has resulted in many variations in formulae and some of the fast papers have sacrificed to some extent their latitude. According to the present invention, itis found that if the paper is pre-coated with certain types of chemicals which have wetting power, the resulting coating with light sensitive material shows higher speed and better latitude. The reasons for this result have not been definitely determined but we believe that greater penetration of the sensitizing solution is at least one factor. The present invention cannot use all types of wetting agents as we have found that certain classes of wetting agents give excellent results whereas others do not give material improvement and in some cases, givepoorer results. In general, most of the wetting agents of the sulfated high molecular alcohol type are unsuitable, some of them, particularly secondary alkyl sulfates, resulting in serious fogging of the background.

We have found that four types of chemical compounds are useful. In order of merit, they are the esters of sulfosuccinicacid with alcohols having more than five carbon atoms, sulfonated terpinyl alkyl phenols, sulfonated higher alkyl phenols and sulfonated alkylated naphthalenes. The reason why these compounds give excellent results and greatly increase the speed of the blueprint or similar sensitized coating has not been definitely determined. It is evident it is not a question purely of ordinary wetting power because some of the commercial wetting agents of the sulfated alcohol type which have been used effectively for many wetting agent purposes do not appear to be suitable. Apparently the chemical nature of the compounds, inaddition to their wetting power, is' a factor. The problem is so complex that we have not found a definite reason of which-we can be certain and accordingly, the invention is not limited to any particular theory of operation. However, we believe that it is probable that one factor may be the difference in'the linkage of the sulfur-oxygen groups. All

of the materials which have been found effective contain sulfonic acid groupings; the materials which have proven less suitable contain for the most part sulfate groupings. It is possible that the sulfate ion may have some chemical effect on the blueprint coating which is not obtained with a sulfonic acid group. This reason is advanced as a possible partial-explanation without limiting the invention thereto.

While it is possible to add the sulfonic wetting 1 agents to the blueprint coating, this is usually not desirable as a'certain precipitation of iron is apt to result. This can be avoided by clarification. Just as good results are obtained by precoating the paper with a'dilute solution of the wetting agent, and this modification is preferred for its practical advantage, although the inven-' tion is not broadly limited thereto.

The present invention gives improved results both with simple blueprint coating formulae of slow speed and with high speed formulae such as,

for example, those described in the copending application of G. Philip Ham, Serial No. 219,599 filed July 16, 1938 now Patent Number 2,165,166

which issued July 4, 1939. The improvement of the present invention is obtained regardless of which formula is used, but, of course, an inherently rapid formula will give greater total speed when treated in accordance with the present invention. It is an advantage of the present invention that it isapplicable to all types of coating formulae.

The invention will be described in detail in conjunction with the specific examples in which a simple slow emulsion is used. The same relative increase in speed is obtained with the inherently more rapid coatings. The parts are by weight.

\ Example I Blueprint paper was treated with a solution containing 0.7 part per thousand of sodium di (methylamyl) sulfosuccinate. Treatment .was effected by passing the paper to be coated over a roller which dipped into the dilute solution of the wetting agent. The treated paper was then coated with a sensitizing formula containing parts of water, 25' parts of ferric ammonium oxalate and 5 parts of potassium ferricyanide. Coating was effected by floating the paper on the surface of a bath of the coating solution, two coatings being given to the paper in this man.- ner, followed by drying atabout 28 C. The paper was ordinary 21 1b., 50% rag stock paper.

the same solution in the identical manner, but not pre-coated with the wetting agent.

Example 2 Blueprint paper as described iii Example 1 is pre-coated with an aqueous solution containing 0.7 part per thousand of the sodium salt of dioctylsulfosuccinic acid, followed by coating as described in Example 1. The results are practically the same as with Example 1.

Example '3 Example 4 The treatment described in Example 1 was carried out using as a wetting agent about 1 part per thousand of the sodium salt of sulfonated alkyl phenols. Results were almost as good in speed and latitude as Examples 1 to 3, and the background was white or only perceptibly bluish.

Example 5 The procedure of Example 1 was'car'ried out using 0.5% aqueous solution of sodium isoprppylnaphthalene sulfonate as the wetting agent. Results were not quite as fast as Example 4, although a marked improvement over the unprecoated paper was noticeable. Backgrounds were white to faintly blue.

Example 6 The procedure of Example 1 was followed in the-pre-coating but instead of employing a slow blueprint emulsion, a high speed blueprint coating was employed such as is described and claimed in the copending application of G. Philip Ham referred to above. by dissolving 20 parts of ferric ammonium oxalate This solution was prepared citric acid were introduced in the order given.

The -final coating solution 'had a pH of 7.7. Coating was by the floating method as described in Example 1.

Test prints showed much greater speed and latitude than paper coated with the same solution without any pre-coating, and the results as far as printing speed and latitude are concerned are superior to Examples 1 to 5, which is to be expected by reason of the inherently greater speed and latitude of the coating solution employed.

What we claim is:

1. A light sensitive coated paper containing a small amount of an ester of sulfosuccinic acid and the light sensitive blueprint coating.

2. A blueprint paper containing a small amount of an ester of sulfosuccinic acid and the light sensitive blueprint coating.

3. A blueprint paper containing a small amount of a dioctyl sulfosuccinate and a light sensitive blueprint coating.

4. A method of coating blueprint paper which comprises subjecting the paper to preliminary treatment with a dilute aqueous solution of an ester of sulfosuccinic acid, and then coating with the blueprint coating.

5. A method of coating blueprint paper which comprises subjecting the paper to preliminary treatment with a dilute aqueous solution of adioctyl sulfosuccinate and then coating with the blueprint coating.

GARNET PHILIP HAM. ROBERT BOWLING BARNES. 

